198 research outputs found
Vacuum energy: quantum hydrodynamics vs quantum gravity
We compare quantum hydrodynamics and quantum gravity. They share many common
features. In particular, both have quadratic divergences, and both lead to the
problem of the vacuum energy, which in the quantum gravity transforms to the
cosmological constant problem. We show that in quantum liquids the vacuum
energy density is not determined by the quantum zero-point energy of the phonon
modes. The energy density of the vacuum is much smaller and is determined by
the classical macroscopic parameters of the liquid including the radius of the
liquid droplet. In the same manner the cosmological constant is not determined
by the zero-point energy of quantum fields. It is much smaller and is
determined by the classical macroscopic parameters of the Universe dynamics:
the Hubble radius, the Newton constant and the energy density of matter. The
same may hold for the Higgs mass problem: the quadratically divergent quantum
correction to the Higgs potential mass term is also cancelled by the
microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability
of the whole quantum vacuum.Comment: 14 pages, no figures, added section on the problem of Higgs mass,
version accepted for the special issue of JETP Letter
Observation of Apparently Zero-Conductance States in Corbino Samples
Using Corbino samples we have observed oscillatory conductance in a
high-mobility two-dimensional electron system subjected to crossed microwave
and magnetic fields. On the strongest of the oscillation minima the conductance
is found to be vanishingly small, possibly indicating an insulating state
associated with these minima.Comment: 4 pages, 3 figures, RevTex
A System for Information Management in BioMedical Studies—SIMBioMS
Summary: SIMBioMS is a web-based open source software system for managing data and information in biomedical studies. It provides a solution for the collection, storage, management and retrieval of information about research subjects and biomedical samples, as well as experimental data obtained using a range of high-throughput technologies, including gene expression, genotyping, proteomics and metabonomics. The system can easily be customized and has proven to be successful in several large-scale multi-site collaborative projects. It is compatible with emerging functional genomics data standards and provides data import and export in accepted standard formats. Protocols for transferring data to durable archives at the European Bioinformatics Institute have been implemented
Performance of Finnish biobanks in nationwide pulmonary carcinoid tumour research
Finnish hospital-integrated biobanks administer millions of formalin-fixed paraffin-embedded tissue samples collected within the clinical diagnostics. According to the Finnish Biobank Act, these samples can be coupled with patients’ clinical follow-up data and the data retrieved from national health registries. We collected a nationwide pulmonary carcinoid tumour series from Finnish biobanks to study prognostic factors as well as to explore how the number of tumours found in the Finnish biobanks corresponds to the number of tumours registered by the Finnish Cancer Registry (FCR). Finnish biobanks identified 88% of the tumours registered by the FCR and were able to deliver 63%. The main reasons for lacking samples were paucity of resected primary tumour tissue, incompatible primary diagnosis, and the absence of tissue blocks in the archives. The main bottleneck in the sample application process was retrieving patient data. Altogether, we received 224 tumour samples with appropriate patient data and identified six prognostic factors for shorter disease-specific survival: age over 56 years at the time of diagnosis, tumour size over 2.5 cm, atypical histology, Ki-67 proliferation index higher than 2.5%, hilar/mediastinal lymph node involvement at the time of diagnosis, and the presence of metastatic disease. In conclusion, the Finnish biobank infrastructure offers excellent opportunities for tissue-based research. However, to be able to develop the biobank operations further, involving more medical knowledge in the sample and data acquisition process is a necessity. Also, when working with tissue samples collected over decades, histological expertise is essential for re-evaluation and re-classification of the samples.</p
Nonlinear effects in microwave photoconductivity of two-dimensional electron systems
We present a model for microwave photoconductivity of two-dimensional
electron systems in a magnetic field which describes the effects of strong
microwave and steady-state electric fields. Using this model, we derive an
analytical formula for the photoconductivity associated with photon- and
multi-photon-assisted impurity scattering as a function of the frequency and
power of microwave radiation. According to the developed model, the microwave
conductivity is an oscillatory function of the frequency of microwave radiation
and the cyclotron frequency which turns zero at the cyclotron resonance and its
harmonics. It exhibits maxima and minima (with absolute negative conductivity)
at the microwave frequencies somewhat different from the resonant frequencies.
The calculated power dependence of the amplitude of the microwave
photoconductivity oscillations exhibits pronounced sublinear behavior similar
to a logarithmic function. The height of the microwave photoconductivity maxima
and the depth of its minima are nonmonotonic functions of the electric field.
It is pointed to the possibility of a strong widening of the maxima and minima
due to a strong sensitivity of their parameters on the electric field and the
presence of strong long-range electric-field fluctuations. The obtained
dependences are consistent with the results of the experimental observations.Comment: 9 pages, 6 figures Labeling of the curves in Fig.3 correcte
Contrasting Cases: The Lotka-Volterra Model Times Three
How do philosophers of science make use of historical case studies? Are their accounts of historical cases purpose-built and lacking in evidential strength as a result of putting forth and discussing philosophical positions? We will study these questions through the examination of three different philosophical case studies. All of them focus on modeling and on Vito Volterra, contrasting his work to that of other theoreticians. We argue that the worries concerning the evidential role of historical case studies in philosophy are partially unfounded, and the evidential and hermeneutical roles of case studies need not be played against each other. In philosophy of science, case studies are often tied to conceptual and theoretical analysis and development, rendering their evidential and theoretic/hermeneutic roles intertwined. Moreover, the problems of resituating or generalizing local knowledge are not specific to philosophy of science but commonplace in many scientific practices—which show similarities to the actual use of historical case studies by philosophers of science
The cognitive integration of scientific instruments: Information, situated cognition, and scientific practice
Researchers in the biological and biomedical sciences, particularly those working in laboratories, use a variety of artifacts to help them perform their cognitive tasks. This paper analyses the relationship between researchers and cognitive artifacts in terms of integration. It first distinguishes different categories of cognitive artifacts used in biological practice on the basis of their informational properties. This results in a novel classification of scientific instruments, conducive to an analysis of the cognitive interactions between researchers and artifacts. It then uses a multidimensional framework in line with complementarity-based extended and distributed cognition theory to conceptualize how deeply instruments in different informational categories are integrated into the cognitive systems of their users. The paper concludes that the degree of integration depends on various factors, including the amount of informational malleability, the intensity and kind of information flow between agent and artifact, the trustworthiness of the information, the procedural and informational transparency, and the degree of individualisation
Why is Behavioral Game a Game for Economists? : The concept of beliefs in equilibrium
The interdisciplinary exchange between economists and psychologists has so far been more active and fruitful in the modifications of Expected Utility Theory than in those of Game Theory. We argue that this asymmetry may be explained by economists' specific way of doing equilibrium analysis of aggregate-level outcomes in their practice, and by psychologists' reluctance to fully engage with such practice. We focus on the notion of belief that is embedded in economists' practice of equilibrium analysis, more specifically Nash equilibrium, and argue that its difference from the psychological counterpart is one of the factors that makes interdisciplinary exchange in behavioral game theory more difficult.Peer reviewe
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